Submarine signaling apparatus



I Dec. 26, 1922. 1,440,361

F. L. HOPWOOD. SUBMARINE SIGNALING 'APPARATUS.

FILED JUNE 6. 1922.

9 l b/L 0 XD I /77'- TDR VEZE:

Patented Dec. 26, 1922.

FRANK LLOYD HOBWOOD, OF WOOD GREEN, LONDON, ENGLAND, ASSIGNOR TO SUB-MARINE SIGNAL COMPANY, OF BOSTON, MASSACHUSETTS.

SUBMARINE SIGNALING APPARATUS.

Application filed June 6, 1922. Serial No. 566,373.

To all whom it may concern:

Be it known that I, FRANK LLOYD Hor- WOOD, a subject of the King ofGreat Britain, residing at 416 Alexandra Park Road, Wood Green, in thecounty of London, England, have invented certain new and usefulImprovements in Submarine Signaling Apparatus, of which the following isa specification.

This invention relates to submarine signaling apparatus of thehydrophone t pe and its chief objects are to increase the e ciency ofreception of submarine sound vibrations, to enable both the sensitivityand the tuning to be varied in a predetermined manner and to obtain andvary the directional properties of the instrument as required.

The accompanying drawing shows in section a hydrophone embodying thisinvention.

The apparatus comprises a casing or central ring 25, on which arecarried flanged rings 23 each of which carries a diaphragm 22 fixedthereto. 24 are diaphragms which are held in place against the centralring 25 by the flanged rings 23, which in turn are held in place byrings 21 that screw on to the central ring 25, 26 being suitable packingrings.

Mounted centrally between the inner pair of diaphragms 24 is a tube 271one end of which receives a bush 28 which slides on through an aperturein one diaphragm and has a flanged head to prevent any inward movementof the bush with respect to the diaphragm. Passing through the otherdiaphragm is a bush threaded on its exterior to recei e the threadedinterior of that end of the tube 27 and which houses the head 29 of ascrew, the threaded part of which engages with a thread in the bush 28.Attached to the tube 27 by threads or otherwise by a suitable dependingpiece 210 is a microphone 211, the leads for which are indicated by 212.

By rotating the head 29 of the screw, the inner pair of diaphragms 24can be brought closer together or can be allowed to move away from eachother, thus altering the distance between the internal and external pairof diaphragms. Or the distance can be variedby screwing up the rings 21more or less tightly, the packings 26 admitting of adjustment throughthe small movements required. Also the air backed surfaces of thediaphragms 28 can be varied in area by introducing into the spacebetween the diaphragms suitable solid (say, gelatine paraffin or rubber)or liquid (say. water, or alcohol) separating medium filling up aproportion of the flat spaces as indicated at 221 for one side of theinstrument, means of access being provided for the introduction of thesubstance, for example by removing the outer. diaphragm.

By varying the distance between the diaphragms or the air backed areasor both, not only are the sensitivity and the tuning varied but bydifferent adjustments at the two sides the directional properties areeontrolled. Thus if the two sides of the instrument are balancedacoustically by adjustments on the lines described the instrument isbidirectional, being most sensitive to waves approaching in eitherdirection along the axis. If the symmetry or balance is slightlydisturbed the instrument becomes unidirectional in a variable degreewhile if the acoustic asymmetry is considerable the instrument becomesnondirectional. of distance and air backing the sharpness of thedirectional properties can beregulated to obtain a maximum effect. I

The whole instrument may be enclosed in jelly or other acousticallytransparent material contained in an outer body of rubber or likematerial and without any air spaces.

\Vhat I claim and desire to secure by Letters Patent of the UnitedStates is- 1. A hydrophone comprising a body, two external diaphragms,two internal diaphragms coupled together and spacially separated fromthe external diaphragms, and means for adjusting the distance be tweenthe internal and external diaphragms.

2. A hydrophone comprising a body, two external diaphragms, two internaldiaphragms coupled together and spacially separated from the externaldiaphragms, and a screw adjustment for varying the distance between theinternal and external diaphragms.

3. A hydrophone comprising a body, two external diaphragms, two internaldiaphragms coupled together and spacially. separated from the externaldiaphragms, and means for varying the acoustic symmetry of theinstrument.

4. A hydrophone comprising a body, two

external diaphragms, two internal diaphragms coupled together andspacially separated from the external diaphragms, and means whereby thedistance between the two pairs of internal and external diaphragms maybe independently adjusted at each side of the instrument.

5. A hydrophone comprising a body, two external diaphragms, two internaldiaphragms coupled together and spacially separated from the externaldiaphragms, and means for varying the acoustic sym metry of theinstrument comprising nongaseous material introduced between the innerand outer diaphragms of at least one pair of diaphragms.

I 6. A hydrophone comprising a body, two external diaphragms, twointernal diaphragms coupled together and spacially separated from theexternal diaphragms, and means for varying the area of the air backedsurfaces of the outer diaphragms comprising non-gaseous materialintroduced between the inner and outer diaphragms of at least one pairof diaphragms.

7. A hydrophone comprising a body, two external diaphragms, two internaldiaphragms coupled together and spacially separated from the externaldiaphragms, means for adjusting the distance between the internal andexternal diaphragms, and means for enclosing said hydrophone containingacoustically transparent non-gaseous material completely surroundingsaid hydrophone without air spaces.

FRANK LLOYD HOllVOOD.

